Medical Factors

Hypoxia—lack of oxygen in the body—the most important thing to remember is that the victim of hypoxia is not aware of his or her condition; the effects are progressive with altitude: lassitude and indifference, belligerence or euphoria, including loss of aircraft control, reduced vision, confusion, inability to concentrate, impaired judgement, slowed reflexes, and eventual loss of consciousness. Symptoms typically appear at 14000’, including the potential loss of aircraft control at 16000’, and unconsciousness at 18000’. Nevertheless, at 10000’ there is a definite but undetectable hypoxia. Prevention: fly above 10000’ for duration of less than 30 minutes, or wear oxygen. At night, hypoxia can impair vision at 5000’, so it is recommended that oxygen be worn at night above this altitude.

Carbon Monoxide Poisoning—susceptibility increases with altitude; symptoms: sluggishness and warmness, intense headache, throbbing temples, ringing in ears, dizziness, dimming of vision, vomiting, and eventual death. If symptoms are noticed, turn off the heat and open a vent.

Decompression Sickness—the build-up of nitrogen bubbles in different parts of the body when they come out of solution as a result of a rapid pressure decrease. The risk is greatest in flight operations above 20000’. The formation of bubbles in the lungs or the brain could give rise to chest pain and/or collapse. If symptoms include dull, sickening pain, an immediate descent to lower altitude is required.

Vertigo—spatial disorientation—loss of bearings or confusion of sense of position and movement that occurs with reduced visual reference (clouds, fog, snow, etc.).

Anaesthetics—after spinal or general anaesthetics, do not fly until your doctor says it is safe; while it is difficult to generalize about local anaesthetics, common sense requires waiting 24 hours before flying.

Blood Donation—Donation of blood disturbs body circulation for several days, which may impair flying; for this reason, active pilots should avoid blood donation; if blood has been donated, a pilot should not fly for 48 hours.